Diffusion-weighted imaging with reverse phase-encoding polarity: the added value to the conventional diffusion-weighted imaging in differentiating acute infarctions from hyperintense brainstem artifacts.

OBJECTIVES

The aim of our study was to assess the value of diffusion-weighted imaging with reverse phase-encoding polarity (R-DWI) in addition to conventional DWI using forward phase-encoding polarity (F-DWI) in differentiating acute brainstem infarctions from hyperintense artefacts.

METHODS

Seventy-six patients with 38 hyperintense brainstem artefacts and 38 acute brainstem infarctions that had undergone F-DWI and R-DWI were retrospectively selected based on the clinicoradiological diagnosis. Four radiologists independently rated their confidence in diagnosing acute infarctions and ruling out brainstem artefacts in a blind manner, and then compared the diagnostic performance and confidence between F-DWI alone and F-DWI with R-DWI.

RESULTS

The areas under the curve determined for F-DWI with R-DWI in diagnosing infarctions were significantly higher than F-DWI alone for all readers (resident 1, 0.908 vs 0.776; resident 2, 0.908 vs 0.789; neuroradiologist, 0.961 vs 0.868; emergency radiologist, 0.934 vs 0.855, all p < 0.05). All readers were more confident using F-DWI with R-DWI than F-DWI alone (all p < 0.05) for diagnosing acute brainstem infarction, and three readers (readers except the neuroradiologist) were more confident using F-DWI with R-DWI for ruling out brainstem artefacts (p ≤ 0.001).

CONCLUSION

The addition of R-DWI to F-DWI is a valuable method for differentiating acute brainstem infarctions from hyperintense artefacts.

KEY POINTS

• Hyperintense brainstem artefacts can be confused with acute infarctions on DWI. • Additional R-DWI to F-DWI reduces inter-reader variability in diagnosing brainstem infarctions. • Additional R-DWI improves performance and confidence for discriminating infarctions from artefacts.